Various architectural coverings are known with systems to compensate for the weight of the blind and improve operation of raising or lowering the blind. In particular, it is known to provide a spring assist module in the head rail of an architectural covering. The spring assist module stores energy when a blind is extended, e.g. lowered and releases this energy to assist in retracting, e.g. raising of the blind, for instance with a roller, drive shaft, lift spool or the like.
US 2005/0217805 describes the use of a spring motor having a spring tape which is wound from a storage shaft onto an output shaft as the blind is lowered. The stored resilient energy in the spring acts to assist in lifting of the blind when the spring tape returns from the output shaft to the storage shaft.
Arrangements such as that described in US 2005/0217805 are undesirably bulky. The present application considers that it would be desirable to provide rails having depths and heights (perpendicular to the elongate length of the rail) no more than 25 mm.
It is thus an object of the present invention to provide a spring assist module of low cost and/or low complexity which can be used with rails of relatively short length and having a small width, i.e. a small height and/or depth.